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Why the larch bud-moth cycle collapsed in the subalpine larch-cembran pine forests in the year 1990 for the first time since 1850
Abstract
The larch bud-moth cycle has been observed in the sub-alpine larch-cembran pine forests 16 times since 1850. Infestation is easily recognized by the characteristic red-brown discoloration of the larch crowns due to the wasteful feeding of the bud moth larvae. The heaviest defoliation recurs at intervals of 8.470.27 (SE) years, and the larval density per kilogram of larch branches varies more than 10000-fold over four or five generations. The basic regulatory mechanism for this cycle is the induced change in food quality for the two or more subsequent larval generations. Defoliation functions as a negative feedback mechanism acting on larval density. In 1989 local discoloration in the Upper Engadine valley was observed in the usual first focus. In 1990 and 1991, however, instead of the expected widespread defoliation damage, larval densities decreased drastically. Based on extensive field data collected from 1961 to 1991 on the development and the survival of the bud moth (Zeiraphera diniana Gn.) and the phenology of the host, Larix decidua L., this paper shows the effect of weather on survival in the egg stage and on the coincidence of larval hatching with the sprouting of the larch. It is shown that the winter and spring weather conditions in 1989–1991 were conducive to unusually high egg mortality. Since these conditions occurred in three successive generations, population growth was effectively reduced and the cycle collapsed prematurely. Thus the rather persistent cyclicity of the larch-larch bud-moth system was disturbed by weather conditions with a very low probability of occurrence, but due to the inherent high resilience of the system, the next population peak with visible defoliation is expected to occur 1996/1997, provided that the weather conditions return to the climatic standard.
... However, it remains unclear how, if at all, climate affects the intensity, frequency, and persistence of cyclic LBM population outbreaks. Though still debatable, previous work suggests increased winter temperatures lead to decreased egg survival during diapause (Baltensweiler 1993), and the temporal offset between larval and foliar development may dampen LBM population growth (Benz 1974;Wermelinger et al. 2018). Moreover, it has been argued that rising temperatures can shift the insect's outbreak epicentres to higher elevations (Johnson et al. 2010). ...
... This unexpected return of outbreaks suggests that phase shifts in the NAO may also have shifted outbreak epicentres back into lower elevations where subalpine larch forests exist (Fig. 4). Furthermore, warm winters may have caused elevated respiration of LBM eggs during diapause leading to a decoupling of LBM with foliar development (Baltensweiler 1993), but recent cold winters may have reversed this trend. Nevertheless, it remains debatable if higher energy consumption during dormancy accelerates egg hatching towards earlier, non-optimal late winter conditions, for which intra-and interannual variation in snow fall and snow coverage add another level of complexity (Williams et al. 2015). ...
... Nevertheless, it remains debatable if higher energy consumption during dormancy accelerates egg hatching towards earlier, non-optimal late winter conditions, for which intra-and interannual variation in snow fall and snow coverage add another level of complexity (Williams et al. 2015). Moreover, warmer winter and spring temperatures (together with increased energy stress) can trigger asynchrony between advanced egg hatch and the expansion of larch foliage (Benz 1974;Baltensweiler 1993;van Asch et al. 2012). Presently, the onset of larch needle growth tends to be earlier in the growing season than it was during most of the years when it was monitored before the mid-1980s (Fig. S2b). ...
The sudden interruption of recurring larch budmoth (LBM; Zeiraphera diniana or griseana Gn.) outbreaks across the European Alps after 1982 was surprising, because populations had regularly oscillated every 8–9 years for the past 1200 years or more. Although ecophysiological evidence was limited and underlying processes remained uncertain, climate change has been indicated as a possible driver of this disruption. An unexpected, recent return of LBM population peaks in 2017 and 2018 provides insight into this insect’s climate sensitivity. Here, we combine meteorological and dendrochronological data to explore the influence of temperature variation and atmospheric circulation on cyclic LBM outbreaks since the early 1950s. Anomalous cold European winters, associated with a persistent negative phase of the North Atlantic Oscillation, coincide with four consecutive epidemics between 1953 and 1982, and any of three warming-induced mechanisms could explain the system’s failure thereafter: (1) high egg mortality, (2) asynchrony between egg hatch and foliage growth, and (3) upward shifts of outbreak epicentres. In demonstrating that LBM populations continued to oscillate every 8–9 years at sub-outbreak levels, this study emphasizes the relevance of winter temperatures on trophic interactions between insects and their host trees, as well as the importance of separating natural from anthropogenic climate forcing on population behaviour.
... Dendrochronologia xxx (xxxx) 126047 breaks occurred during the last 1200 years at high elevation (> 1'300 m asl) (Iyengar et al., 2016;Esper et al., 2007). After the 1980 s regular cycles disappeared, potentially related to climate change (Baltensweiler, 1993;Esper et al., 2007;Büntgen et al., 2009). The first major outbreak since then was reported in 2018 at many alpine locations again . ...
... Larch growth at the same site was clearly affected by GLBM outbreaks until 1980 (Büntgen et al., 2009;Hartl-Meier et al., 2017), potentially even causing higher resource availability for spruce during strongest GLBMinduced growth limitation of larch. Some outbreaks after cold winters suggest cold temperature-related egg survival during diapause enhancing outbreaks in the subsequent growth period (Baltensweiler, 1993;Büntgen et al., 2020b). Also, in Val Müstair outbreaks disappeared after the 1980 s probably due to warming-induced phenological mismatch between larval and foliar development (Esper et al., 2007). ...
The European Dendroecological Fieldweek (EDF) is a one-week course that takes place every year at varying locations in Europe according to the principle “Bring tree-ring research to the people”. The EDF welcomes early-career to advanced researchers, but also forest service and other federal agency employees and private people interested in tree-ring sciences from all over the world. It encompasses a large spectrum of dendrochronological field, laboratory and data analysis methods and scientific fields including climatology, ecology, physiology, geomorphology and archaeology. Multiple scales of observations from the individual cell to the ecosystem level and from seasonal to multi-centennial periods are covered. Work on mini research projects in topic groups alternates with keynote lectures and individual participants’ presentations.
As one of the first in-person tree-ring meetings since the start of the COVID-19 pandemic the 31st EDF was held in summer 2021 in Val Müstair, Switzerland. Topics included i) Tree age and climate sensitivity of a relict, old-growth Scots pine stand, ii) Blue intensity-based climate sensitivity of Norway spruce growth, iii) Tree rings as indicators of grey larch budmoth outbreaks, iv) Growth of larch trees along an abandoned irrigation channel, v) Wood anatomical characteristics of two alpine creeping shrub species, and vi) Historical dating of a stable and a residential house. Alongside with their educational value these projects allowed novel insight into the age structure and growth dynamics of the sub-alpine forests and beyond in the valley and provided valuable outcome to the local stakeholders such as the Nature Park Biosfera Val Müstair, the local forest service and the public of Val Müstair.
Under hindered conditions due to the pandemic, the 31st EDF still demonstrated its strength as an international educational and interdisciplinary scientific field and lab course, combining teaching with the application of cutting-edge technologies.
... Cyclic occurrence is typical for many insect defoliators. Some have been returning periodically since centuries, such as Zeiraphera dinianaI, which displays extraordinary regularity in its cycles ( Figure 2-2) (Baltensweiler 1993, Virtanen and Neuvonen 1999, Esper et al. 2007). Zeiraphera diniana is considered the most dangerous pest of subalpine larch forests, presumably due to the luxurious feeding of the larvae, leading to desiccation and the typical red-brown discoloration of needles (Baltensweiler et al. 2008). ...
... Similarly, a reduction in the nutritional quality of host plants may lead to decreased growth rates, reduced fecundity and survival of the biotic agents. Finally, climatic changes may result in lost synchronisation between the biotic agent and its host plant, resulting in less risk of Zeiraphera diniana (Baltensweiler 1993, Esper et al. 2007). ...
Forest ecosystems are currently facing rapidly expanding new environmental conditions as a result of climatic and anthropogenic changes. While disturbances have always been an important part of the natural forest ecosystems dynamics allowing regeneration, the scale and nature of these disturbances are causing concern. They are mainly challenging traditional forest management practices, often aimed at maintaining or restoring past conditions. Such choices need serious re-assessment, since they could create forests that
are ill-adapted to current conditions, and more susceptible to disturbances. The recent endorsement of sustainable forest management in Europe goes in that direction.
This report provides a synthesis of the risks caused by biotic agents to EU forests, with the aim to provide managers and policy-makers with the current evidence-base and tools to fight these risks. Most work so far has usually focused on a specific type of biotic agent, or a restricted geographical extent. This has led to a sometimes segmented view of the problem, and a synthesis of the recent advances is timely.
... Climate change can also decrease the ability of tree species to tolerate insect herbivory, causing an increased impact of outbreaks on forests (Baltensweiler, 1993). ...
... In addition, climate is often modulated by large-scale oceanic and atmospheric modes and circulation patterns , such as the El Niño-Southern Oscillation (ENSO), causing locally different responses of insect population dynamics to climate. Some studies have revealed an increase in the frequency and intensity of insect outbreaks in response to climate change (Thom and Seidl, 2016), while others revealed recurring outbreaks may be disrupted or diminished (Baltensweiler et al., 1993). Regionally and locally different responses of insect outbreaks to ENSO and climate have been investigated in several regions including the southeastern United J o u r n a l P r e -p r o o f States (Woli et al., 2014), Patagonia (Paritsis and Veblen, 2011), Chile (Estay and Lima, 2010) and Malaysia (Kishimoto-Yamada et al., 2009). ...
Insect outbreaks are key disturbances triggering decline episodes in humid subtropical evergreen forests in eastern China. However, their long-term variability and linkages to climate are still unclear largely due to the shortness of records reporting forest damage. A retrospective approach would improve our understanding of long-term outbreak variability and its dependence on climate and relevant atmospheric circulation patterns such as the El Niño-Southern Oscillation (ENSO). This study provides a dendrochronological reconstruction of Dendrolimus punctatus outbreaks affecting Pinus massoniana in humid subtropical eastern China. We used tree-ring width and carbon isotope data from sites where outbreaks were or not were reported for the past fifty years, here considered as host and non-host sites, respectively. The results showed that inter-annual changes in carbon isotope discrimination are more sensitive to outbreaks than changes in tree-ring width. Based on carbon isotopes, we inferred that photosynthetic rates increased as a compensatory mechanism in response to insect defoliation. We reconstructed eleven insect outbreaks since 1915, which corresponded to ENSO positive phases and below-average sea surface temperatures in the central and eastern tropical Pacific Ocean. These conditions correspond to “La Niña” episodes which induce hot and dry climate conditions across the study region and these may facilitate the occurrence of D. punctatus outbreaks.
... The outbreak intensity is high in 1962, 1971, and 1979 and much lower in 1996, 2006, and 2015. Such weakening of the LBM outbreaks since 1981 has been already noted by several authors (Baltensweiler, 1993;Battipaglia et al., 2014;Saulnier et al., 2017). ...
... Our results confirm the recent perturbations of the LBM cycle observed in different regions of the Alps, with a weakening of the outbreaks since the 1980s (Baltensweiler, 1993;Battipaglia et al., 2014;Saulnier et al., 2017). The last outbreak we observed occurred mainly in 2015 and 2016 at 2000 and 2200 m.a.s.l. ...
Larch budmoth (LBM) periodically defoliates alpine stands of European larch during vast outbreaks occurring generally at 8–10 year intervals. LBM outbreaks recently declined and the ongoing global warming has been pointed out as a possible cause of this decline. In this article, we reconstructed the recent history of LBM outbreaks at different elevations along a larch elevational gradient in the French Alps using direct and indirect observations based on tree-ring width and density analysis, and compared it with local climatic data. We found that LBM outbreaks time-series were better reconstructed with latewood density than with ring width. We also found that there was a recent but limited elevational shift of LBM outbreaks from medium toward higher elevations. We suggest that this elevational shift is a consequence of the variable effect of the global warming at the different elevations. Winter warming is expected to affect differently the timing of LBM egg hatch as well as that of larch bud flush, larvae being at present susceptible to emerge whereas no needles are available as food at the former optimal elevation. A better synchronization between larch and LBM may exist at higher elevations.
... Mineral nutrients have essential and specific functions in plant metabolism leading to normal plant growth and crop production (Mengel and Kirkby, 1987). Food quality plays vital roles in mediating the foraging behaviour, growth and reproductive performance, as well as population dynamics of herbivorous insects (Martinat, 1987;Mattson and Haack, 1987;Stamp and Bowers, 1990;Ayres, 1993;Baltensweiler, 1993;Stamp, 1993), including K. lacca. Poor nutrient content in host plants can have an adverse effect on the performance and fitness of sap feeders (McNeill and Southwood, 1978;Dixon, 1985;Denno et al., 1986;Cook and Denno, 1994). ...
... Highest number of lac insects at crop maturity in the treated hosts was due to the better food quality that was provided by nutrient management of Z. mauritiana. Food quality plays central role in mediating the growth, reproduction and population dynamics of herbivorous insects (Martinat, 1987;Mattson and Haack, 1987;Stamp and Bowers, 1990;Ayres, 1993;Baltensweiler, 1993;Stamp, 1993). Mean number of lac insects at crop maturity was higher in the present study in comparison to the previous study and it might be credited to the better management of the host tree. ...
... In years of high population densities, larvae may completely defoliate larch canopy leaves and this defoliation occurs synchronously over large areas, although rarely triggering tree mortality (Baltensweiler et al., 1977). Several mechanisms have been proposed to explain LBM oscillations, including behavioural changes in population quality (Baltensweiler, 1993), bud mothdisease interactions (Anderson and May, 1980) and host-parasitoid interactions (Turchin et al., 2003). However, it remains unclear how these cycles are modulated by climatic influences (Esper et al., 2007). ...
... Historical records (Baltensweiler and Rubli, 1999) and tree-ring based reconstructions (Esper et al., 2007;Büntgen et al., 2009) documented that larch bud moth (LBM) outbreaks have been recurring with a high degree of regularity every 8-10 years in the European Alps. Surprisingly, the amplitude of regular LBM mass outbreaks has been greatly diminished since the early 1980s, which was associated to exceptional warming climate during the recent decades (Baltensweiler, 1993;Ims et al., 2008;Johnson et al., 2010). Due to the unprecedented warming during recent decades, the region favourable for LBM outbreaks appears to have shifted to elevations beyond the upper limit of larch occurrence (Johnson et al., 2010). ...
... Climate change has direct and indirect effects on insects, thereby influencing forest structure and composition at broad scales ( Figure 2). Indirectly, changing temperature and precipitation regimes will influence the spatial distribution of host trees and their suitability to herbivorous insects, for example, because host defenses are compromised and phenological markers, such as bud break, are disrupted resulting in a phenological mismatch (Baltensweiler, 1993;Anderegg et al., 2015). Community associates that influence insect population success, including pathogens, fungi, natural enemies and competitors, will also be influenced by climatic changes, thereby having both positive and negative indirect effects on outbreaks of forest insects and pathogens (Sturrock et al., 2011;Addison et al., 2015;Kalinkat et al., 2015;Kolb et al., 2016). ...
... Desynchronization of evolved insect traits with host tree phenology was also shown to occur. The larch bud moth (Zeiraphera diniana) relies on a crucial timing of egg hatch with host tree bud break, and warm spring temperatures disrupt the timing, resulting in reduced population growth (Baltensweiler, 1993). Invasive species with limited phenotypic plasticity in new habitats could be vulnerable to both desynchronization of seasonality and with host tree phenology. ...
Forests and trees throughout the world are increasingly affected by factors related to global change. Expanding international
trade has facilitated invasions of numerous insects and pathogens into new regions. Many of these invasions have caused substantial
forest damage, economic impacts and losses of ecosystem goods and services provided by trees. Climate change is already affecting
the geographic distribution of host trees and their associated insects and pathogens, with anticipated increases in pest impacts
by both native and invasive pests. Although climate change will benefit many forest insects, changes in thermal conditions
may disrupt evolved life history traits and cause phenological mismatches. Individually, the threats posed to forest ecosystems
by invasive pests and climate change are serious. Although interactions between these two drivers and their outcomes are poorly
understood and hence difficult to predict, it is clear that the cumulative impacts on forest ecosystems will be exacerbated.
Here we introduce and synthesize the information in this special issue of Forestry with articles that illustrate the impacts of invasions of insects and pathogens, climate change, forest management and their
interactions, as well as methods to predict, assess and mitigate these impacts. Most of these contributions were presented
at the XXIV IUFRO World Congress in 2014.
... Esper et al. (2007) linked the absence of outbreaks since the late 20 th Century to the period of extreme regional warmth outside of the climatic envelope of the past 1200 years, suggesting that a temperature variation threshold has recently been passed. Baltensweiler (1993), who examined the reasons for the collapse of the 1990 outbreak, agreed that consecutively warmer winters and springs affected the ability of the moth to outbreak. Both studies suggested that the increased winter and spring temperatures affected the overwintering eggs by inducing early development and egg hatch, leading to increased mortality of eggs when colder weather hit again or increased 1 st instar larvae starvation and mortality when they hatched before budburst in their host. ...
... Asynchrony due to climate change is likely a significant factor in the absence of outbreaks by the larch budmoth, as the species must hatch simultaneously with the flushing of the larch in the spring or otherwise experience high rates of mortality (Baltensweiler 1993). The pine processionary moth, however, is one of the exceptions to the need for synchrony. ...
... Certain factors have been hypo thesized, such as changes in densitydependent fac tors (Fischlin & Baltensweiler 1979, Bjornstad et al. 2002, Turchin et al. 2003, Johnson et al. 2004. A decline in the intensity of LBM outbreaks and a lack of spatial synchrony have been observed across the European Alps since 1981 (Baltensweiler 1993). A possible reason for this and comparable collapses of population cycles might indeed be direct and/or indirect effects of global warming (Esper et al. 2007, Kress et al. 2009, Johnson et al. 2010. ...
... Two cores per tree were taken at breast height (~1.3 m above surface) from 20−27 individuals of larch and pine trees per site to guarantee the subsequent development of robust tree-ring chronologies. Pine is normally a non-host species for the common dark form of LBM (Baltensweiler 1993, which can be a valuable reference species to help disentangle the effect of insect defoliation on TRW from that of adverse climatic conditions (Dormont et al. 2006, Büntgen et al. 2009). ...
ABSTRACT: The intensity of cyclic larch budmoth ( Zeiraphera diniana GuenÈe; LBM) outbreaks across the European Alps has been reported to have weakened since the early 1980s. In addition to a warmer climate, changes in land-use cover over modern and historical times may have affected the LBM system. Here, we present tree-ring-based reconstructions of LBM outbreaks from a mixed subalpine larch-pine forest in the French Alps for the period 1700-2010. Temporal variation in LBM outbreak severity was mainly driven by land-use changes, including varying forest structure and species composition. Human population pressure and associated resource demands for fuel wood and construction timber not only resulted in a reduction of larch and subsequent suppression of pine, but also supported an overall grassland expansion for livestock. Superimposed on modern land abandonment and pine re-colonization is a strong warming trend, which may also contribute to the observed late 20th-century weakening of Alpine-wide cyclic LBM outbreaks. Our results suggest that a complex interplay of different factors triggered less synchronized LBM outbreaks at broader scales, with overall significantly lower intensities at local scales.
... Population outbreaks of forest insects are conspicuous events as they often result in large-scale defoliation of forests (Baltensweiler 1993;Jepsen et al. 2011;Kayes and Tinker 2012). The spatial delineation of outbreaks in alpine forests is in many cases tied to topographical features such as altitude (Baltensweiler 1993;Kamata 2002;Kharuk et al. 2007;Schott et al. 2010) and the transitions between affected and unaffected areas may be abrupt (Hunter et al. 1991;Raymond et al. 2002;Hagen et al. 2007). ...
... Population outbreaks of forest insects are conspicuous events as they often result in large-scale defoliation of forests (Baltensweiler 1993;Jepsen et al. 2011;Kayes and Tinker 2012). The spatial delineation of outbreaks in alpine forests is in many cases tied to topographical features such as altitude (Baltensweiler 1993;Kamata 2002;Kharuk et al. 2007;Schott et al. 2010) and the transitions between affected and unaffected areas may be abrupt (Hunter et al. 1991;Raymond et al. 2002;Hagen et al. 2007). The adjacency of areas with contrasting dynamics offers opportunities for testing hypotheses about which mechanisms promote versus inhibit population outbreaks (Maron et al. 2001;Raymond et al. 2002). ...
Outbreaks of geometrid defoliators in subarctic birch forest in Fennoscandia often occur at high altitude in a distinct zone along the tree line. At the same time, moth larvae may not have an impact on the forest at lower altitude. Directly adjacent outbreak and nonoutbreak areas offer unique opportunities for studying the underlying mechanisms of outbreaks. Within two altitudinal gradients in coastal northern Norway, we investigated whether altitudinal outbreaks might be caused by release from pupal predation by ground-dwelling invertebrates such as harvestmen (Opiliones), spiders (Araneae), rove beetles (Coleoptera: Staphylinidae), carabid beetles (Coleoptera: Carabidae), and other beetles (Coleoptera). We predicted a consistently higher abundance of such generalist predators at low versus high altitudes. Our results did not support this prediction. There was no consistent altitudinal variation in the abundance of predators that could be related to zonal moth outbreaks in the birch forest slopes. In addition, none of the predator groups investigated showed any numerical response to a distinct outbreak of winter moth that took place during the course of the study. Consequently, localised moth outbreaks at the altitudinal tree line in northern Norway cannot be explained by the release from pupal predation by the predator groups examined here. Résumé—Des éclosions massives de géométridés défoliateurs dans les forêts subarctiques de bouleaux de Fennoscandie se produisent souvent à haute altitude dans une zone distincte le long de la ligne des arbres. Au même moment, les larves des lépidoptères peuvent être sans impact sur la forêt à une altitude inférieure. Ces zones directement adjacentes avec et sans éclosions représentent des occasions uniques pour étudier les mécanismes sous-jacents aux éclosions. Sur deux gradients d'altitude sur la côte nord de la Norvège, nous avons vérifié si les éclosions saisonnières pouvaient être dues à la réduction de la prédation des nymphes par les invertébrés vivant au sol, tels que les opilions (Opiliones), les araignées (Araneae), les staphylins (Coleoptera: Staphylinidae), les carabes (Coleoptera: Carabidae) et les autres coléoptères (Coleoptera). Nous avons prédit des densités toujours plus élevées de ces prédateurs généralistes aux basses altitudes qu'aux altitudes plus élevées. Nos résultats n'appuient pas cette prédiction. Il n'existe pas de variation régulière de l'abondance des prédateurs en fonction de l'altitude qui pourrait être mise en relation avec les éclosions dans des zones particulières le long des pentes des forêts de bouleaux. De plus, aucun des groupes de prédateurs étudiés n'a montré de réponse numérique à une éclosion bien marquée de l'arpenteuse tardive survenue au cours de l'étude. En conséquence, il n'est pas possible d'expliquer les éclosions localisées de lépidoptères au niveau de la ligne des arbres dans le nord de la Norvège par la réduction de la prédation des nymphes par les groupes de prédateurs examinés dans notre étude.
... For example, tree ring analysis shows that outbreaks of C. occidentalis do not occur in years of drought, whereas C. fumiferana tends to outbreak in dry springs (Lynch 2012). A breakdown in cycles of the LBM was attributed to warm springs followed by cool summers (Baltensweiler 1993), whereas Kress et al. (2009) found that defoliation by the LBM was associated with cool summers. This is impossible to interpret. ...
... ntioned above, widespread synchronization of the onset of the growing season and leafing of birch was apparently related to outbreaks of AMs and WMs ( Jepsen et al. 2009). This could have acted through synchronization of egg hatch and budburst. In several cases the impact of mismatch between egg hatch and bud burst has been tested exper- imentally. Baltensweiler (1993) modified the hatch of LBM eggs through shading. Delayed hatch in a warm spring synchronized the larvae beneficially with bud burst, whereas early hatch was detrimental . For GMs, delayed egg hatch was advantageous overall because even though food quality was poor for late-hatching larvae, this reduced their density and they experienced ...
A quarter century ago, the question was posed of whether a general hypoth-esis could explain population cycles of forest Lepidoptera. Since then, con-siderable progress has been made in elucidating mechanisms associated with cyclic dynamics of forest Lepidoptera. Delayed density-related parasitism and reduced fecundity during population peaks are common influences on population dynamics, although why fecundity declines is not understood. The hypothesis that sunspots explain cycles is rejected. The influences of delayed-induced plant defenses on populations are inconsistent, but interac-tions between plant chemistry, pathogens, and immunity remain rich areas for future study. Population dynamics of forest Lepidoptera can be syn-chronous over large geographic scales, and repeatable waves of spread of outbreaks occur for some species. Climate warming could modify species dis-tributions and population cycles, but mechanisms have not been elucidated and changes in cyclic dynamics are not generally apparent. Integration of top-down and bottom-up influences on cyclic dynamics and quantification of dispersal are necessary for progress in understanding patterns of insect outbreaks.
... The important temporal coincidence of egg hatch and needle-flush is well buffered at subalpine altitudes by the radiation climate. Eggs hibernating underneath the black lichens on branches exposed to direct solar radiation hatch 14 to 20 days before eggs exposed on the north side of the trees (Bovey 1966, Baltensweiler 1984, 1993. First instar larvae install themselves successfully within the closed fascicles of needles 5Á8 mm in length. ...
... More recent analyses (Baltensweiler 1993) suggest this pattern was probably due to the alternating sequence of favourable and unfavourable late winter and spring weather. Such weather either increases egg survival or induces catastrophic egg mortality, and may also influence larch growth selectively, depending on the site location. ...
Tree-ring analysis of insect-defoliated trees has so far been used for detecting past insect outbreaks only. We hypothesize that the impact of the larch-bud-moth (LBM) Zeiraphera diniana outbreaks on the growth of larch Larix decidua in the Engadine (Switzerland) is closely coupled to the spatial development of the outbreak and the ecological characteristics of the respective sites and weather conditions. We tested this hypothesis by reviewing data sets available in the literature and by analysing original data. We monitored LBM population densities and the needle phenology, growth and defoliation of larch over 28 years, i.e. over four outbreak cycles. In addition, information on defoliation patterns covering six earlier outbreaks over 50 years was matched with tree-ring information. Tree-ring chronologies of 18 larch stands were analysed with regard to abrupt growth changes and latewood events. Defoliation induces an immediate reduction in latewood, followed by a reduction in needle length and a significant decrease in radial growth in the subsequent year. We have called this tree-ring pattern the ''larch-bud-moth syndrome''. A careful analysis of the various parameters of the LBM syndrome for two specific population cycles enabled us to define different interaction patterns between weather conditions and tree growth. These can then be included in climate change models to help disentangle the impact of insect defoliation from that of adverse climatic conditions.
... However, we do not definitively regard it as an LBM outbreak at our sites, as we do not consider the sum of our observations clear enough. In the 1990 case, the initial larvae counts in the Swiss Alps matched the growth reduction, but a mass outbreak finally failed and no visible defoliation was recorded, most probably due to too warm winter temperatures [10,62]. In our data, the 1990 event was only detected at sites close to the treeline, which is corroborated by the fact that LBM epicenters would move upward in a warmer climate [63]. ...
Though frequently used in dendroclimatology, European larch (Larix decidua Mill.) is regularly defoliated by mass outbreaks of the larch budmoth (Zeiraphera griseana Hb., LBM). The near-cyclic growth depressions are unrelated to but possibly coincide with cold summers, which challenges signal detection on interannual timescales. LBM defoliation events cause sharp maximum latewood density declines and irregular earlywood/latewood ratios in the outbreak year, followed by one or two anomalously narrow rings. Here, we present a process-based method integrating these diverse response patterns to identify and distinguish LBM-related signals from climate-induced deviations. Application to larch sites along elevational transects in the Swiss Alps reveals the algorithm to perform better than existing extreme event detection methods, though our approach enables additional differentiation between insect- and climate-induced signatures. The new process-based multi-parameter algorithm is a suitable tool to identify different causes of growth disturbances and will therefore help to improve both tree-ring-based climate and insect defoliation reconstructions.
... Moreover, cycles of larch budmoth population interaction have been reported by many researchers (cf. [5,6,7,8,9,10,11]). Due to seasonal variation (non-overlapping generations) in the interaction related to larch budmoth, it is more appropriate to model such interaction with discrete-time systems of host-parasitoid type. ...
... More broadly, research on the impact of climate change on other cyclic species of forest Lepidoptera shows that changes in their dynamics are often related to altered distributions. For example, the cycles of the larch budmoth Zeiraphera diniana (Baltensweiler, 1993) collapsed in the 1980s in the Swiss Alps, which was associated with a warming-related shift in the elevation range of the species (Johnson et al., 2010). The winter moth (Operophtera brumata) has moved further north and west in Fennoscandia as the climate has warmed (Jepsen et al., 2013;Vindstad et al., 2022). ...
Understanding how climate warming will influence species interactions is a key question in ecology and predicting changes in the prevalence of disease outbreaks is particularly challenging. Ectotherms are likely to be more influenced by climatic changes as temperature governs their growth, feeding, development, and behavior. We test the hypothesis that pathogen transmission and host mortality will increase at warmer temperatures using a cyclic forest insect, the western tent caterpillar (WTC), Malacosoma californicum pluviale, and its baculovirus. The virus causes population declines at peak host density. WTC are gregarious and clustering is predicted to increase the risk of within family infection; however, how temperature influences this has not been examined. We investigated the impact of temperature on different components of the transmission process in order to pinpoint the possible mechanisms involved. In the laboratory, leaf consumption increased linearly with rising temperature between 15 and 30°C. Insects died more rapidly from virus infection as temperature increased, but this did not translate into differences in the production of viral transmission stages. To examine the influence of temperature on virus transmission, we created a temperature difference between two greenhouses containing potted red alder trees, Alnus rubra. The cooler greenhouse (mean 19.5°C) was roughly similar to ambient temperatures in the field, while the warmer greenhouse was 10°C higher (mean 29°C). As predicted, both larval movement and feeding were higher at the warmer temperature, while the likelihood of the preinfected, inoculum larvae dying on the tents was twice as high in the cooler greenhouse. This resulted in increased virus mortality and a higher transmission parameter under cooler conditions. Therefore, we suggest that, contrary to our prediction, the reduced movement of infected larvae at colder temperatures increased the risk of infection in these gregarious insects and had a greater impact on virus transmission than the increased activity of the susceptible larvae in warmer conditions. Long‐term population data from the field, however, show no relationship between temperature and infection levels, suggesting that local changes in virus transmission might not scale up to population infection levels.
... Larch budmoth, larch tortrix Range: Europe, China, Korea, Japan, Russia, N. America (Baltensweiler et al. 1977;Baltensweiler 1993aBaltensweiler , 1993bBjørnstad et al. 2002;Peltonen et al. 2002;Dormont et al. 2006;Esper et al. 2007;Kress et al. 2009;Iyengar et al. 2016 (Daniel and Myers 1995;Parry 1995;Parry et al. 1997;Rothman and Roland 1998;Cooke and Roland 2000;Parry et al. 2001;Cooke and Roland 2003;Parry et al. 2003;Wood et al. 2009;Trudeau et al. 2010;Wood et al. 2010;Charbonneau et al. 2012;Cooke et al. 2012;Moulinier et al. 2013;Hughes et al. 2015;Uelmen et al. 2016 ...
One of the most significant categories of insect that cause damage to trees are the defoliators. While many orders of insects feed on tree foliage, in this chapter we will focus on Lepidoptera, as there are so many Lepidopteran larvae (caterpillars) that are known for their extensive tree damage. In this chapter we review the impact of foliage feeders on forest trees and stand composition, and the ways in which densities of these species or the defoliation they cause are monitored. We do not cover insects attacking ornamental trees in the landscape, nor do we cover insects feeding exclusively on foliage tips or buds.
... The decadal means of reconstructed temperatures before and after the LBM correction were compared, focusing mainly on the extended cool periods. Low-temperature conditions favor LBM growth, and therefore impact trees significantly (Baltensweiler, 1993). We first calculated the deviation of the temperature series from the overall (1711-2020) mean, then employed Student's t-test to compare the mean in moving 11-year resolution. ...
Insect outbreaks are proven to harm trees, reducing their biomass accumulation due to the defoliation of leaves during the growing season. Various defoliators are responsible for the formation of extremely narrow tree rings in different tree species. In climate reconstructions based on tree-ring width, such narrow rings are often considered as noise, because their formation is not entirely caused by climatic conditions. Thus, the impact of defoliators should be removed (nullified) for unbiased climate reconstructions. This study mainly describes a statistical approach to disentangle the effects of Larch budmoth(LBM) (Zeiraphera diniana) and climate for an unbiased temperature reconstruction in the Bai-Ma mountain area in Southwest China using Larix potaninii. After applying our new approach, growth-climate relationships improved significantly (p
... Changes in natural ecosystems-both terrestrial and marine, change of habitat of fauna and flora, changed patterns of insect pest outbreak cycles, etc.-have been observed, and these are believed to have occurred as a consequence of the changed climate. [1][2][3][4] It is, thus, of extreme interest and importance to know whether and when the next drastic change in the climate is likely to occur. If the rate of variation in concentrations of greenhouse gases in the atmosphere continued to follow the present trend, could one predict when Earth's climatic system would tip over irreversibly to a new dynamical state? ...
Increased levels of greenhouse gases in the atmosphere, especially carbon dioxide, are leading contributors to a significant increase in the global temperature, and the consequent global climatic changes are more noticeable in recent years than in the past. A persistent increased growth of such gases might lead to an irreversible transition or tipping of the Earth's climatic system to a new dynamical state. A change of regimes in CO 2 buildup being correlated to one in global climate patterns, predicting this tipping point becomes crucially important. We propose here an innovative conceptual model, which does just this. Using the idea of rate-induced bifurcations, we show that a sufficiently rapid change in the system parameters beyond a critical value tips the system over to a new dynamical state. Our model when applied to real-world data detects tipping points, enables calculation of tipping rates and predicts their future values, and identifies thresholds beyond which tipping occurs. The model well captures the growth in time of the total global atmospheric fossil-fuel CO 2 concentrations, identifying regime shift changes through measurable parameters and enabling prediction of future trends based on past data. Our model shows two distinct routes to tipping. We predict that with the present trend of variation of atmospheric greenhouse gas concentrations, the Earth's climatic system would move over to a new stable dynamical regime in the year 2022. We determine a limit of 10.62 GtC at the start of 2022 for global CO 2 emissions in order to avoid this tipping.
... On the other hand, several other authors reported cycles for larch budmoth interaction (cf. Esper et al. (2007); Konter et al. (2015); Baltensweiler and Fischlin (1988); Baltensweiler (1993); Berryman (1996); Battipaglia et al. (2014); Turchin (2003)). Due to climate change and nonoverlapping breeding of larch budmoth, it is suitable to model such interactions with parasitoid-host type iterative maps. ...
Cyclic types of ecological dynamics have been found in several biological species of forest Lepidoptera. There are several possible reasons for this, for example, interactions with consumers, predators, plant quality index, and interactions of density-dependent type. Furthermore, interaction with consumers and plant quality index is regarded as key ingredients to alter the dynamics for the parasitoid population. Consequently, the quality of food resources fluctuates due to the level of herbs. Such changes have been observed in different systems of forest pests. Lepidoptera (larch budmoth) is a destructive worm that affects high-altitude trees around the world and is rapidly declining and becoming extinct in large areas of the forest. Considering the interaction between the budmoth and plant quality index for larch trees in the mountain range in Switzerland (Swiss Alps), we discuss the dynamics of a discrete-time system. Ivlev type functional response regarding plant quality index is used for the formulation of discrete-time model concerning the interaction between the index of plant quality and budmoth. Moreover, the existence of steady-states, their local behaviors, and the boundedness of solutions are carried out for the discrete-time model under consideration. It is investigated that the model undergoes flip bifurcation about coexistence by applying the theory of normal forms and the center manifold theorem. Furthermore, the direction and the existence of Hopf bifurcation are explored for the model around its coexistence. Various methods of controlling chaos have been introduced to avoid system fluctuations and bifurcating attitudes. Validation of the analytical findings is illustrated through numerical simulations. Finally, the analytical results are validated by experimental and actual field data.
... The findings reported in this study clearly showcase the large potential of P. cembra for dendroclimatic purposes. Last but not least, it seems worthwhile to mention that P. cembra is a non-host species for the larch budmoth (LBM; Baltensweiler, 1993;Nola et al., 2006) which affects L. decidua trees cyclically (each 8-9 years; Baltenschweiler et al., 1977;Esper et al., 2007) to defoliate their needles. Insect defoliation thereby leads to markedly reduced ring increments and mass over two to five years (Kulman, 1971;Battipaglia et al., 2014;Arbellay et al., 2018;Castagneri et al., 2020) due to a reduction of the tree's photosynthetic capacity and the related suppression of tree growth due to lower carbon assimilation and the heavy reliance on carbohydrate reserves to replace foliage (Gleason and Ares, 2004;Myers and Kitajima, 2007). ...
Tree rings form the backbone of high-resolution palaeoclimatology and represent one of the most frequently used proxy to reconstruct climate variability of the Common Era. In the European Alps, reconstructions were often based on tree-ring width (TRW) and maximum latewood density (MXD) series, with a focus on European larch. By contrast, only a very limited number of dendroclimatic studies exists for long-lived, multi-centennial Pinus cembra, despite the widespread occurrence of the species at treeline sites across the European Alps. This lack of reconstructions can be ascribed to the difficulties encountered in past studies in extracting a robust climate signal from TRW and MXD chronologies. In this study, we tested various wood anatomical parameters from P. cembra as proxies for the reconstruction of past air temperatures. To this end, we measured anatomical cell parameters and TRW of old-growth trees from the God da Tamangur forest stand, known for being the highest pure, and continuous P. cembra forest in Europe. We demonstrate that several wood anatomical parameters allow robust reconstruction of past temperature variability at annual to multidecadal timescales. Best results are obtained with maximum latewood radial cell wall thickness (CWTrad) measured at 40 μm radial band width. Over the 1920–2017 period, the CWTrad chronology explains 62 % and >80 % of interannual and decadal variability of air temperatures during a time window corresponding roughly with the growing season. These values exceed those found in past work on P. cembra and even exceed the values reported for MXD chronologies built with L. decidua and hitherto considered the gold standard for dendroclimatic reconstructions in the European Alps. The wood anatomical analysis of P. cembra records therefore unveils a dormant potential and opens new avenues for a species that has been considered unsuitable for climate reconstructions so far.
... The findings reported in this study clearly showcase the large potential of P. cembra for dendroclimatic purposes. Last but not least, it seems worthwhile to mention that P. cembra is a non-host species for the larch budmoth (LBM; Baltensweiler, 1993;Nola et al., 2006) which affects L. decidua trees cyclically (each 8-9 years; Baltenschweiler et al., 1977;Esper et al., 2007) to defoliate their needles. Insect defoliation thereby leads to markedly reduced ring increments and mass over two to five years (Kulman, 1971;Battipaglia et al., 2014;Arbellay et al., 2018;Castagneri et al., 2020) due to a reduction of the tree's photosynthetic capacity and the related suppression of tree growth due to lower carbon assimilation and the heavy reliance on carbohydrate reserves to replace foliage (Gleason and Ares, 2004;Myers and Kitajima, 2007). ...
... However, the future dynamics of these isolated populations are still uncertain as they could both expand their range due to the limitation of anthropogenic pressure and increasing temperature (Vittoz et al., 2008) or retreat, due to water limitations and competition with other taxa (Lyu et al., 2019). Despite being very suitable for investigating the climate-growth relationship, as they are rarely affected by biotic disturbances (e.g., defoliators and bark beetle outbreaks) compared to European larch (Larix decidua Mill.) or Norway spruce (Baltensweiler, 1993;Carrer et al., 2007;Saulnier et al., 2011), to our knowledge, only a few studies assessed the long-term intra annual climate sensitivity of this typical treeline species at the edge of its distribution (Carrer et al., 2018) and none have investigated it in combination with wood density measurements (that are rarely performed in this species). ...
High-elevation ecosystems are one of the most sensitive to climate change. The analysis of growth and xylem structure of trees from marginal populations, especially the ones growing at the treeline, could provide early-warning signs to better understand species-specific responses to future climate conditions. In this study, we combined classical dendrochronology with wood density and anatomical measurements to investigate the climate sensitivity of Pinus cembra L., a typical European high-elevation tree species distributed in isolated patches in the Carpathians. Samples were collected from the Retezat Mountains, South-Western Romania. We analyzed ring width (TRW), maximum density (MXD), xylem anatomical traits [cell number per ring (CNo), cell density (CD), conduit area (CA), and cell wall thickness (CWT)] time series, split into ring sectors and assessed the relationships with monthly and daily climate records over the last century (1901–2015). The analysis showed a strong dependency of TRW on CNo and MXD on CWT. Summer temperature positively correlated with MXD and CWT [monthly correlation (r) were 0.65 and 0.48 respectively] from the early to late wood but not TRW (r = 0.22). CA positively correlated with water availability (r = 0.37) and negatively correlated with temperature (r = −0.39). This study improves our general understanding of the climate–growth relationships of a European high-elevation tree species and the results could be considered for forecasting population dynamics on projected changes in climate.
... These alterations in LBM food quality trigger the collapse of the LBM population and create the remarkably regular 8-10 year periodicity of LBM outbreaks that had been observed for 1200 years. Switzerland's forest service had documented regular LBM outbreaks since 1864 (Baltensweiler 1993;Baltensweiler et al. 2008). However, since the 1980s, no alpine-wide synchronized LBM outbreak event has occurred. ...
Understanding long-term insect and pathogen effects on host tree physiology can help forest managers respond to insect and pathogen outbreaks, and understand when insect and pathogen effects on tree physiology will be exacerbated by climate change. Leaf-level physiological processes modify the carbon (C) and oxygen (O) stable isotopic composition of elements taken up from the environment, and these modifications are recorded in tree-rings (see Chaps. 10.1007/978-3-030-92698-4_9 , 10.1007/978-3-030-92698-4_10 , 10.1007/978-3-030-92698-4_16 and 10.1007/978-3-030-92698-4_17 ). Therefore, tree-ring stable isotopes are affected by both the tree’s environment and the tree’s physiological responses to the environment, including insects and pathogens. Tree-ring stable isotopes provide unique insights into the long-term effects of insects and pathogens on host tree physiology. However, insect and pathogen impacts on tree-ring stable isotopes are often overlooked, yet can substantially alter interpretations of tree-ring stable isotopes for reconstructions of climate and physiology. In this chapter, we discuss (1) the effects of insects(defoliators, wood-boring, leaf-feeding), pests (parasitic plants), and pathogens(root and foliar fungi) on hostphysiology (growth, hormonal regulation, gas exchange, water relations, and carbon and nutrient use) as they relate to signals possibly recorded by C and O stable isotopes in tree-rings, (2) how tree-ring stable isotopes reveal insect and pathogen impacts and the interacting effects of pathogens and climate on hostphysiology, and (3) the importance of considering insect and pathogen impacts for interpreting tree-ring stable isotopes to reconstruct past climate or physiology.
... Indirekt werden veränderte Temperatur-und Niederschlagsregime die räumliche Verteilung von Wirtsbäumen und deren Eignung für herbivore Insekten und Pathogene beeinflussen, zum Beispiel weil die Abwehrkräfte der Wirtsbäume beeinträchtigt werden oder weil phänologische Anpassungen (z. B. zum Entfalten der Knospen) gestört werden (Baltensweiler 1993, Anderegg et al. 2015. Interaktionen von Pathogenen, Pilzen, natürlichen Feinden und Konkurrenten, die den Erfolg von Insektenpopulationen beeinflussen, werden ebenfalls durch klimatische Veränderungen beeinflusst und haben damit sowohl positive als auch negative indirekte Auswirkungen auf Ausbrüche von Waldinsekten und Pathogenen (Sturrock et al. 2011, Kalinkat et al. 2015, Kolb et al. 2016. ...
Der Klimawandel verändert unsere Wälder auf vielfältige Weise. Dabei werden negative Auswirkungen auf die Wälder, ihre Ökosystemleistungen und die Waldwirtschaft höchstwahrscheinlich überwiegen. Neben dem Anstieg der Temperatur und Änderung der Niederschlagsverteilung sind es vor allem die Zunahme von Extremereignissen und ihren Interaktionen, die zu erheblichen Störungen der Wälder führen werden. Die weit verbreiteten, massiven Waldschäden infolge der trockenen und heißen Jahre 2018 – 2019 haben bereits angedeutet, mit welcher Geschwindigkeit diese Veränderungen auch in Deutschland voranschreiten können. Daher erscheint es dringend geboten, umfassende Konzepte zu entwickeln, um die Wälder und ihre Bewirtschaftung so anzupassen, dass negative Folgen möglichst weit abgepuffert werden können, um auch in Zukunft die vielfältigen Ökosystemleistungen der Wälder für unsere Gesellschaft bereitzustellen. Wie beim Klimaschutz ist auch bei der Anpassung an den Klimawandel die Politik gefordert, Rahmenbedingungen zu schaffen, die im Sinne der Generationengerechtigkeit zukünftigen Generationen die gleichen Optionen für die Nutzung der Wälder bieten wie der heutigen Generation. Ebenso wie der Klimaschutz stellt die Anpassung der Wälder eine dringliche und massive Herausforderung für alle Beteiligten dar, die Paradigmenwechsel auf vielen Ebenen erfordert. Vor diesem Hintergrund hat der Wissenschaftliche Beirat für Waldpolitik (WBW) das vorliegende Gutachten erstellt.
Die Erstellung des Gutachtens erfolgte auf der Basis geprüfter wissenschaftlicher Erkenntnisse und richtet mit seinen Handlungsempfehlungen den Fokus auf die wesentlichen Einflussmöglichkeiten zur Aufrechterhaltung und Verbesserung der Bereitstellung der Ökosystemleistungen des Waldes im Klimawandel. In dem Gutachten werden zunächst die derzeit bekannten Auswirkungen der Klimaänderungen auf Wälder und ihre Ökosystemleistungen skizziert und die Anpassungsmöglichkeiten in unterschiedlichen Bereichen der Bewirtschaftung und Nutzung der Wälder aufzeigt. Diese Bereiche umfassen die Waldwirtschaft, Holzverarbeitung, Bioökonomie, Naturschutz, Bodenschutz, Gewässerschutz, Gesundheitsvorsorge, Erholung und Tourismus. Die daraus gezogenen Schlussfolgerungen münden in konkrete Handlungsempfehlungen für die Anpassung in insgesamt 13 Handlungsfeldern. Ziel der Empfehlungen ist es, Bedingungen dafür zu schaffen, dass Ökosystemleistungen der Wälder auch zukünftig entsprechend des gesellschaftlichen Bedarfs bereitgestellt werden können.
Zu diesem Zweck sollten Wälder, wo nötig, durch waldbauliche Unterstützung hin zu diversen, resilienten und anpassungsfähigen Wäldern entwickelt werden. Dies umfasst die aktive und passive Förderung der Vielfalt standortangepasster Baumarten und ihrer funktionalen und genetischen Diversität ebenso, wie den Schutz der Waldböden und ihrer Funktionen, die mit angepassten Maßnahmen erhalten und verbessert werden müssen. Hierzu werden konkrete Maßnahmen zur Anpassung von Waldbeständen, insbesondere in den Phasen der Verjüngung und Bestandespflege empfohlen, die mit verbesserten regionalen und überregionalen Daten zur Standorts- und Baumarteneignung unterstützt werden müssen.
Biodiversität im Wald ist eine wichtige Grundlage für die Anpassungsfähigkeit und Vielfalt aller Prozesse, welche die Ökosystemfunktionen und -leistungen erst ermöglichen. Sie muss bei der Anpassung der Wälder an den Klimawandel daher von der genetischen bis zur Ökosystemebene umfassend berücksichtigt werden. Hier stellt sich insbesondere die Frage, welche Arten, Populationen und Lebensräume am stärksten gefährdet sind und in welchem Umfang sich diese mit dem Klimawandel verschieben werden bzw. verschieben können. Der Schutz der Biodiversität sollte daher auf ganzer Fläche, also auch außerhalb von Schutzgebieten berücksichtigt werden. Ein besonderes Augenmerk sollte daher auf die zukünftige Struktur und Baumartenzusammensetzung der Wälder gelegt werden. Natürliche Biotope, Habitate und Ökosysteme sind im Rahmen der Anpassung auf Landschaftsebene so weit wie möglich zu erhalten und zu fördern. Durch die Förderung von Biotopverbünden sollen die Bewegungsmöglichkeiten von Arten gewährleistet werden; bei wenig mobilen Arten sollte die Möglichkeit gezielter Ansiedlungen in zukünftigen Verbreitungsgebieten genutzt werden. Ein repräsentatives Biodiversitätsmonitoring und die Berücksichtigung des Klimawandels bei der Entwicklung von Schutzzielen sollen einen möglichst effizienten Naturschutz im Wald ermöglichen.
Der Erhalt der Wälder und ihrer vielfältigen Ökosystemleistungen hängt ganz erheblich von ihrem Schutz gegenüber biotischen und abiotischen Risiken ab, die in Zukunft zunehmen werden. Daher bedarf es eines deutlich verbesserten Risikomanagements in enger Verknüpfung mit einem zeitlich und räumlich hoch aufgelösten Monitoring, dem eine Schlüsselstellung im Anpassungsprozess der Wälder zugeschrieben wird. Zur Abwehr großflächiger Schäden in Wäldern bedarf es in Ergänzung des betrieblichen
Waldschutzes eines überregionalen Waldschutzmanagements, einer verbesserten Kontrolle von Schadorganismen und Waldkrankheiten, einer objektiven Schadensbewertung und Risikovorsorge aber auch der Forcierung restaurativer Maßnahmen zum Waldumbau.
Zunehmende Extremwetterereignisse, eine Reduktion der Produktivität der Wälder und Veränderungen im Baumartenspektrum werden bei gleichzeitig steigenden Kosten für Anpassung, Risikomanagement, Monitoring und die Bereitstellung von Ökosystemleistungen die Erträge aus der traditionellen Waldbewirtschaftung mit Fokus auf Rohholzproduktion langfristig reduzieren. Diese Entwicklungen verschärfen die ohnehin schon bestehenden strukturellen Probleme vor allem im kleinparzellierten Privat- und Körperschaftswald. Um vor diesem Hintergrund Anpassungsmaßnahmen effektiv umsetzen zu können, bedarf es der Schaffung stabiler institutioneller Strukturen, die die angemessene Betreuung des Nichtstaaatswaldes einschließt, und einer effizienteren Gestaltung der forstlichen Förderung. Dies sollte flankiert werden durch den Aufbau von Informationsplattformen, der Schaffung von Anreizen zur aktiven Waldbewirtschaftung und Bildung von größeren Bewirtschaftungseinheiten.
Mit der zu erwartenden Verringerung der Produktivität der Wälder und Verschiebung der Baumartenzusammensetzungen hin zu mehr Laubholz wird langfristig die Versorgung mit dem Rohstoff Holz insbesondere aus heimischen Wäldern eine große Herausforderung. Dies erfordert auch eine Anpassung der nachgelagerten Holzwirtschaft und Holzverwendung. Dafür müssen Wertschöpfungsketten etabliert werden, die die wirtschaftliche und klimawirksame Nutzung von Holzrohstoffen aus heimischer Waldbewirtschaftung optimieren und die Transformation zu einer Bioökonomie als Grundlage neuer umweltfreundlicher Produkte stützen. Anreizsysteme und technische Verfahren sollten entwickelt werden, die zur Erhöhung der stofflichen und Verringerung einer direkten energetischen Nutzung führen, insbesondere bei bisher schwer zu vermarktenden Holzsortimenten (Kalamitätsholz, Nadelstarkholz, Laubholz). Eine zentrale Rolle spielt dabei der Holzbau als unmittelbar verfügbare Brückentechnologie1 im Klimaschutz und zur Schonung endlicher Rohstoffe. Um die in Zukunft
1 Mit Brückentechnologie ist hier gemeint, dass der Holzbau aktuell die einzige anwendungsreife Technologie (negative emission technology) ist, die es ermöglicht, Kohlenstoff in nennenswertem Umfang außerhalb von Ökosystemen zu speichern. „Brücke“ bedeutet hierbei, dass diese Technologie deshalb ab sofort eingesetzt werden sollte, um diese Kohlenstoffspeicherung umzusetzen bis in der Zukunft möglicherweise andere Technologien wie beispielsweise carbon capture and storage oder carbon capture and usage Technologien in eine Anwendungsreife (TRL 9) kommen. Dies bedeutet nicht, dass danach der Holzbau keine Bedeutung mehr hat, aber der Begriff unterstreicht die Dringlichkeit, diese Möglichkeit der Kohlenstoffspeicherung sofort einzusetzen.im Inland zurückgehende Bereitstellung von Nadelholzsortimenten teilweise ersetzen zu können, müssen Voraussetzungen für die Generierung neuer Holzstoffquellen aus Gebraucht- und Altholz geschaffen realisiert werden. Um langfristig eine ausreichende Versorgung mit Nadelholz sicherzustellen, sollte ein risikoarmer Anbau klimaangepasster Nadelbaumarten in Mischbeständen erfolgen. Temporäre Marktverwerfungen nach großflächigen Störungen sollte mit reaktionsfähigen Märkten und entsprechenden Logistik- und Lagerstrukturen entgegengewirkt werden.
Wälder sind eine wichtige Grundlage sogenannter kultureller Ökosystemleistungen. Die Attraktivität von Wäldern für die Freizeit- und Erholungsnutzung im Zuge der erwarteten klimatischen Veränderungen wird wahrscheinlich weiterhin zunehmen. Gleichzeitig kommt es zu Veränderungen gewohnter Wald- und Landschaftsbilder und zu veränderten Voraussetzungen für verschiedenste Freizeitaktivitäten im Wald. Die Bereitstellung von Erholungsleistungen und Reduktion möglicher Konflikte zwischen Erholungsnutzung und der Holzernte steigert den Aufwand der Waldbewirtschaftung, gerade in den urbanen Räumen. Eine Honorierung der Ökosystemleistungen für Erholung, Sport und Tourismus ist daher neben kommunikativen und konfliktmindernden Maßnahmen ein wichtiger Baustein zur zukünftigen Gestaltung von klimaresilienten Erholungswäldern.
Die notwendigen Maßnahmen zur Aufrechterhaltung und Verbesserung der Bereitstellung von Ökosystemleistungen der Wälder sind sehr umfangreich und kostenintensiv. Nach Einschätzung des WBW übersteigen die Aufwendungen für eine rasche und effektive Anpassung der Wälder an den Klimawandel deutlich ein Niveau, das man vom nicht-staatlichen Waldbesitz im Rahmen der Gemeinwohlverpflichtung des Eigentums erwarten kann. Gegenwärtig beruhen die Einnahmen der Forstbetriebe fast ausschließlich auf Erlösen aus dem Holzverkauf, wohingegen die Bereitstellung der bisher nicht honorierten, gesellschaftlich wichtigen Ökosystemleistungen für Klimaschutz, Wasserschutz, Naturschutz, Erholung etc. als Lasten wahrgenommen werden. Daher ist eine zentrale Empfehlung dieses Gutachtens, dass die öffentliche Hand Vergütungssysteme für die Ökosystemleistungen des Waldes schafft, die den Forstbetrieben langfristig planbare Einnahmen aus der Bereitstellung von Ökosystemleistungen ermöglichen. Eine grundsätzliche und effiziente Möglichkeit hierfür sehen wir darin, nicht einzelne Ökosystemleistungen separat zu honorieren, sondern die Grundlage für die zukünftige Erbringung aller Ökosystemleistungen, die Anpassungsfähigkeit2 der Wälder an den Klimawandel, als Leistung zu betrachten. Empfohlen wird daher eine am Zustand der Wälder orientierte Zahlung, die als eine notwendige Ergänzung der derzeit gängigen maßnahmenorientierten Förderung gesehen wird.
Der rasch voranschreitende Klimawandel beschleunigt die Erosion der Relevanz des bisherigen Erfahrungswissens und führt zu einer Zunahme von Unsicherheiten. Um die Anpassung von Wäldern, Wald- und Holzwirtschaft und anderen relevanten Sektoren an den Klimawandel effektiv und effizient zu gestalten, wird eine Stärkung forstwissenschaftlicher, wald- und holzproduktbezogener Forschung empfohlen. Dabei geht es insbesondere um eine strategische Ausrichtung und die Entwicklung neuer Forschungsansätze im Sinne einer Nachhaltigkeitsforschung, die sich an Dringlichkeit, Lösungsorientierung und Implementierung ausrichtet. Dafür werden entsprechend langfristig angelegte Forschungsinfrastrukturen und Kapazitäten ebenso benötigt wie eine bessere Vernetzung und Kooperation zwischen bestehenden Forschungseinrichtungen.
Zur Beförderung des Transformationsprozesses spricht der WBW darüber hinaus Empfehlungen zu Änderungen in der Aus- und Weiterbildung, den Kommunikationsstrategien, sowie zur Beseitigung von Anpassungshemmnissen und -konflikten in den verschiedenen Bereichen aus.
... Moreover, cycles of larch budmoth population interaction have been reported by many researchers (cf. [6][7][8][9][10][11][12]). Due to seasonal variation (non-overlapping generations) in the interaction related to larch budmoth, it is appropriate to model such interaction with discrete-time systems of host-parasitoid type. ...
Keeping in mind the interactions between budmoths and the quality of larch trees located in the Swiss Alps (a mountain range in Switzerland), a discrete-time model is proposed and studied. The novel model is proposed with implementation of a nonlinear functional response that incorporates plant quality. The proposed functional response is validated with real observed data of larch budmoth interactions. Furthermore, we investigate the qualitative behavior of the proposed discrete-time system with interactions between budmoths and the quality of larch trees. Proofs of the boundedness of solutions, and the existence of fixed points and their topological classification are carried out. It is proved that the system experiences period-doubling bifurcation at its positive fixed point using the center manifold theorem and normal forms theory. Moreover, existence and direction for the torus bifurcation are also investigated for larch budmoth interactions. Bifurcating and fluctuating behaviors of the system are controlled through utilization of chaos control strategies. Numerical simulations are presented to demonstrate the theoretical findings. At the end, theoretical investigations are validated with field and experimental data.
... The LBM outbreak events have been shown to decrease biomass accumulation of the host forests (Peters, Klesse, Fonti, & Frank, 2017). LBM defoliation events can be detected in the annual rings of their larch host trees (Büntgen, Liebhold, et al., 2020;Rolland, Baltensweiler, & Petitcolas, 2001) Secondly, a weakening of the intensity of regular outbreaks from the early 1980s onwards (Baltensweiler, 1993), which corresponds with a European-wide temperature increase (Büntgen et al., 2011;Büntgen, Liebhold, et al., 2020). The ecophysiological mechanism(s) of LBM population dynamics are, however, still not fully resolved. ...
Research into global change ecology is motivated by the need to understand the role of humans in changing biotic systems. Mechanistic understanding of ecological responses requires the separation of different climatic parameters and processes that often operate on diverse spatiotemporal scales. Yet most environmental studies do not distinguish the effects of internal climate variability from those caused by external, natural (e.g. volcanic, solar, orbital) or anthropogenic (e.g. greenhouse gases, ozone, aerosols, land‐use) forcing factors.
We suggest extending the climatological concept of ‘Detection and Attribution’ (DA) to unravel abiotic drivers of ecological dynamics in the Anthropocene. We therefore apply DA to quantify the relative roles of natural versus industrial temperature change on elevational shifts in the outbreak epicentres of the larch budmoth (LBM; Zeiraphera diniana or griseana Gn.); the classic example of a cyclic forest defoliating insect.
Our case study shows that anthropogenic warming shifts the epicentre of travelling LBM waves upward, which disrupts the intensity of population outbreaks that occurred regularly over the past millennium in the European Alps. Our findings demonstrate the ability of DA to detect ecological responses beyond internal system variability, to attribute them to specific external climate forcing factors and to identify climate‐induced ecological tipping points.
In order to implement the climatological concept of ‘Detection and Attribution’ successfully into modern global change ecology, future studies should combine high‐resolution paleoenvironmental reconstructions and state‐of‐the‐art climate model simulations to inform inference‐based ecosystem models.
A free Plain Language Summary can be found within the Supporting Information of this article.
... Cependant durant la pullulation de 1990, les populations se sont effondrées. Ceci serait à mettre sur le compte de la hausse des températures hivernales qui auraient provoqué une mauvaise synchronisation entre l'insecte et son hôte en levant la diapause des oeufs de tordeuse du mélèze trop tôt (Baltensweiler, 1993). ...
Sous les latitudes tempérées, les aires de distribution respectives des espèces d’insectes sont généralement conditionnées par les températures hivernales au travers de seuils minimaux de tolérance pour la survie et le développement. Ainsi, le déplacement des aires de répartition est un des effets les plus notables du réchauffement climatique sur les espèces sensibles au froid. Cependant, les conséquences de la colonisation de nouveaux milieux par les espèces en expansion, notamment sur les interactions interspécifiques restent largement inexplorées. La processionnaire du pin est un ravageur d’origine méditerranéenne, dont l’aire de répartition s’est considérablement étendue vers le nord et en altitude ces deux dernières décennies. Cette expansion est liée à la hausse des températures hivernales qui permet une meilleure survie des colonies se développant durant cette période. Notre étude s’est développée autour de deux axes de recherches : (1) la réponse des ennemis naturels à l’expansion de leur hôte ; (2) l’impact de la colonisation sur une espèce protégée inféodée à la même ressource alimentaire, l’Isabelle de France. Nos résultats ont montré que dans les zones nouvellement colonisées, la processionnaire du pin est libérée de la pression de ses parasitoïdes oophages. Ainsi, au niveau du front d’expansion, une femelle de processionnaire du pin produira plus de descendants que dans le coeur de son aire de répartition. De plus, la défoliation par la processionnaire du pin a un effet négatif sur le développement des chenilles d’Isabelle de France. Nos résultats contribuent à comprendre les causes de l’expansion de ce ravageur forestier et ses conséquences sur les espèces autochtones des zones nouvellement colonisées.
... obs.), phenology shifts in T. pityocampa should be largely decoupled from its host. Consequently, global warming is unlikely to lead to increasing asynchronization, in contrast with predictions for many phytophagous insects on herbs, deciduous trees, and flowers or seeds (Baltensweiler 1993, Buse and Good 1996, Peñuelas et al. 2002. ...
Diplôme : Diplôme de l'Ecole des Hautes Etudes en Sciences Sociales
... The LBM, a moth belonging to Lepidoptera and characterized by periodic cyclic population fluctuations (Dormont et al. 2006), has been studied since the early 1960s in the Engadin valley (Switzerland), and reports of outbreaks in several Alpine areas date back to 1815 (Baltensweiler & Rubli 1999). LBM population cycles are driven by trophic and non-trophic factors, such as host-parasite interactions, food quality, maternal effect, population density and climate (Baltensweiler 1993, Ginzburg & Taneyhill 1994, Berryman 1996, Turchin et al. 2003. The diet of LBM larvae is based on the raw fiber and protein in new larch foliage (Baltensweiler & Fischlin 1988, Berryman 1996, Turchin et al. 2003). ...
The larch budmoth (Zeiraphera diniana Gn.-LBM) offers a unique example of cyclic fluctuations in insect populations. During regular LBM mass outbreaks, defoliation of European larch (Larix decidua Mill.) subalpine trees results in distinct ring-width reductions in the host trees. Although several observations, reconstructions and models suggest that LBM outbreaks travel from the southwest to the northeast along the Alpine arc, gaps in the underlying data still hamper our mechanistic understanding of the spatio-temporal system dynamics. Evidence of historical LBM outbreaks before 1964 is generally associated with uncertainty and is particularly scarce for the Central Italian Alps. Here, we introduce four new larch ring-width chronologies from Val di Sole in the Central Italian Alps and use time-series analyses and comparisons with non-host trees (Picea abies Karst.) to reconstruct LBM mass outbreaks. We identify distinct fingerprints of 15 spatially-synchronized LBM events that occurred between 1774 and 1964 CE. Our results are important for improving qualitative space-time models to simulate travelling wave dynamics of insect populations, and for correcting ring-width-based summer temperature reconstructions from this part of the Alpine arc.
... Many forest Lepidoptera, particularly those found in temperate forests are outbreaking species (Ginzburg & Taneyhill, 1994;Berryman, 1996;Myers & Cory, 2013). During outbreaks, larvae reach such high densities that they cause serious damage to host plants, resulting in large-scale defoliation (Baltensweiler 1993;Jepsen et al. 2011;Kayes & Tinker, 2012). Outbreaks for some Lepidoptera species follow regular cycles (May, 1974), such as the larch budmoth (Zeiraphera diniana), with a predictable outbreak every 8.64 ± 0.29 years (Baltensweiler et al., 1977), but there appears to be no obvious pattern to other outbreaks. ...
The oak processionary moth (Thaumetopoea processionea; OPM) is an invasive pest species that was introduced to West London in 2006. Its gregarious larvae pose a risk to forestry and public health by defoliating oak trees and shedding toxic setae. It is not known how OPM populations will spread or what impact they will have in the UK, therefore the aim of this thesis was to explore the population ecology of oak processionary moth in West London.
The thesis focuses on three key topics. Firstly how habitat influences the temporal and spatial distribution of OPM populations. Secondly, the development of molecular methods to identify the parasitoids of OPM. Thirdly, the characterisation of interactions between OPM and its main parasitoid, Carcelia iliaca. These topics were addressed by a combination of a two-year field study at three sites in West London and lab based molecular techniques.
Oak processionary moth was found to have a strong spatially and temporally stable habitat preference for open woodland containing a high proportion of oak trees. Fieldwork and molecular techniques revealed a new tachinid fly in the UK, C. iliaca, a major parasitoid of OPM. Carcelia iliaca was responsible for the mortality of around 37% of moth pupae on average, suggesting that currently parasitism is not having a stabilising effect on OPM populations.
OPM exhibited similar habitat preferences to continental populations as well as other processionary moths, likely driven by tree apparency. It is not clear how parasitism of OPM would respond in an outbreak and current parasitism rates are lower than those in continental populations. This may be a result of OPM nest removal, which was common management practice at the time of the study. The findings of this study have been used to recommend that nests remain in situ for longer, to allow C. iliaca numbers to increase.
Other OPM management options include tree felling, pesticide application and biocontrol. This study found no evidence that OPM control currently warrants tree felling. Biocontrol could be augmented with the use of specific parasitoids such as the newly discovered C. iliaca or entomopathogenic agents identified in Chapter 3, and may be the favoured management option for stakeholders and managers, but is difficult to manage in the long term.
... The amplitude of outbreaks of larch budmoth also declined in the late 1980s. This was attributed to a disruption of the phenology of egg hatch and leaf development ( [31] and discussed in [5]) and changes in the elevation for optimal population growth [32]. In addition, prediapause temperatures in the autumn influence survival and vigour of larvae before egg hatch such that warm temperatures are detrimental. ...
Population cycles are one of nature's great mysteries. For almost a hundred years, innumerable studies have probed the causes of cyclic dynamics in snowshoe hares, voles and lemmings, forest Lepidoptera and grouse. Even though cyclic species have very different life histories, similarities in mechanisms related to their dynamics are apparent. In addition to high reproductive rates and density-related mortality from predators, pathogens or parasitoids, other characteristics include transgenerational reduced reproduction and dispersal with increasing-peak densities, and genetic similarity among populations. Experiments to stop cyclic dynamics and comparisons of cyclic and noncyclic populations provide some understanding but both reproduction and mortality must be considered. What determines variation in amplitude and periodicity of population outbreaks remains a mystery.
... However, in the southern portion of the species range, budburst may remain unchanged or may be delayed due to a lack of chilling hours needed to satisfy bud dormancy requirements (Harrington and Gould 2015). Changes in host phenology may result in desynchronization of host and pathogen and thus reduce or enhance the impact of pathogens (Baltensweiler 1993, Ramsfield et al. 2016. The phenology of Douglas-fir is well studied, and models can provide relatively accurate estimates of growth initiation and cessation based on variables such as forcing and chilling hours (Campbell and Sorensen 1973, Harrington et al. 2010, Gould et al. 2011, Ford et al. 2016); however, insufficient information is available to model the phenology of spore dispersal for P. gaeumannii and Rhabdocline spp. ...
Seed-source movement trials using common garden experiments are needed to understand climate, tree (host), and pathogen interactions. Douglas-fir (Pseudotsuga menziesii var menziesii) is an important tree species native to western North America influenced by the foliar fungi Phaeocryptopus gaeumannii, a biotroph and causal agent of Swiss needle cast (SNC), and Rhabdocline species, necrotrophs that cause Rhabdocline needle cast. We used the Douglas-fir Seed-Source Movement Trial, a large provenance study of Douglas-fir that consists of populations and test sites chosen to represent the range of climate conditions experienced by Douglas-fir west of the Cascade and northern Sierra Nevada Mountains, USA, to assess disease severity and symptom expression in Douglas-fir in relation to climatic differences between test sites and population sources. Using generalized linear mixed models, probability of disease severity/expression was modeled with respect to the climate variables May through September precipitation (MSP), mean winter temperature (MWT), and continentality. Stark differences in disease expression were observed in trees from different regions, especially in relation to resistance to Rhabdocline spp. and tolerance to P. gaeumannii. There were no major differences across seed-source regions at any particular site in infection levels of P. gaeumannii assessed by fruiting body abundance, yet disease tolerance followed similar geographic patterns as resistance to Rhabdocline spp. Transfers of populations from low to high MSP, and/or cool to warm MWT, increased the probability of moderate to severe Rhabdocline spp. infection and SNC disease symptoms. Our results suggest that local seed sources are adapted to local climate and pathogen pressures and that seed sources from regions with high foliage disease pressure are most resistant/tolerant to those foliage diseases. We also confirm that temperature and precipitation are important epidemiological factors in forest disease and that assisted migration must take into account trophic interactions of trees. Movement of seed sources from dry spring and summer and/or cool winter conditions to mild, mesic environments is likely to lead to increased probability of losses due to these foliage diseases.
... New, punctuated reproduction may overwhelm mechanisms maintaining populations below threshold levels. Alternatively, pest populations may not only fail to increase, but also may crash owing to asynchronous pest and host conditions and new interactions preventing offspring survival (Baltensweiler, 1993). For example, new continuous production of overlapping life stages may increase the effectiveness of Sasajiscymnus tsugae (Coleoptera: Coccinellidae) introduced for biocontrol, possibly limited because it is unable to complete development on aestivating nymphs and early-instar A. tsugae (Salom et al., 2001). ...
... In species undergoing a winter diapause, metabolic reserves (such as triacylglycerides, glycogen, and storage proteins of the hexamerin family) are typically synthesised and accumulated in the fat bodies in the autumn, and then used variously as sources of energy for diapause maintenance, cryoprotectant metabolism and water balance, and eventually for resuming development or activity upon the arrival of favourable conditions (Tauber et al., 1986;Danks, 1987;Leather et al., 1993;Denlinger, 2002). High overwintering mortality occurs when populations have not been able to sequester sufficient reserves before wintering or when winter conditions are especially unsuitable (Baltensweiler, 1993;Han & Bauce, 1998;Sgolastra et al., 2011). In addition, some effects of suboptimal wintering may be apparent only at later stages of the life cycle. ...
... In species undergoing a winter diapause, metabolic reserves (such as triacylglycerides, glycogen, and storage proteins of the hexamerin family) are typically synthesised and accumulated in the fat bodies in the autumn, and then used variously as sources of energy for diapause maintenance, cryoprotectant metabolism and water balance, and eventually for resuming development or activity upon the arrival of favourable conditions (Tauber et al., 1986;Danks, 1987;Leather et al., 1993;Denlinger, 2002). High overwintering mortality occurs when populations have not been able to sequester sufficient reserves before wintering or when winter conditions are especially unsuitable (Baltensweiler, 1993;Han & Bauce, 1998;Sgolastra et al., 2011). In addition, some effects of suboptimal wintering may be apparent only at later stages of the life cycle. ...
1. Diapause is a dynamic process of low metabolic activity that allows insects to survive periods of harsh conditions. Notwithstanding the lowered metabolism, and because diapausing insects have no access to food, diapause has an energetic cost that may affect post‐diapause performance.
2. Previous studies on the solitary bee Osmia lignaria have shown that prolonged pre‐wintering periods (the time during which individuals already in diapause remain at warm temperatures) are associated with elevated lipid consumption, fat body depletion, and body weight loss. The present study investigated whether prolonged pre‐wintering also affects reproduction, i.e. whether the costs associated with diapause could have an effect on post‐diapause performance in this species.
3. Females were exposed to a range of pre‐wintering conditions, and ovary development and individual post‐wintering performance were monitored throughout their adult life span.
4. No evidence of an effect of pre‐wintering duration on post‐diapause reproductive success was found. Expected differences in the timing of establishment were not observed because ovary maturation was, surprisingly, not arrested during pre‐wintering. Prolonged pre‐wintering duration did not result in decreased life span, probably because emerging females could rapidly replenish their metabolic reserves through feeding. However, there was a very strong effect of the duration of the pre‐emergence period on the likelihood of nest establishment.
5. Longevity, the main factor determining fecundity in Osmia , is subjected to high levels of intrinsic variability, even among females of similar size exposed to identical conditions during development and nesting.
... Cependant durant la pullulation de 1990, les populations se sont effondrées. Ceci serait à mettre sur le compte de la hausse des températures hivernales qui auraient provoqué une mauvaise synchronisation entre l'insecte et son hôte en levant la diapause des oeufs de tordeuse du mélèze trop tôt (Baltensweiler, 1993). ...
Under temperate latitudes, low temperature is usually a key factor constraining the distribution of insects species through minimal thresholds required for survival and development. Thus, range shift is one of the striking effects of global warming observed in a number of cold- sensitive species. However, the consequences of such range shifts on inter-specific interactions are largely unexplored. The winterdeveloping pine processionary moth originated from the Mediterranean Basin but expanded considerably its range distribution towards higher latitudes and altitudes over the last two decades. This range expansion is clearly associated with better winter survival and enhanced feeding activity related to climate warming. Two research topics were developed in our study : (1) the response of natural enemies to an expanding host ; (2) the impact of the colonisation of new areas on an endangered moth species exploiting the same host tree, the Spanish moon moth. Our results show that in newly- colonized areas, pine processionary moth is released from its egg-parasitoids. Thus, near the expansion front, a female pine processionary moth will have more offspring than in the core of its distribution range. Moreover, previous tree defoliation by the pine processionary moth has a negative effect on the development of Spanish moon moth larvae. Our results contribute to understand the causes of the expansion of this forest pest and its consequences on species previously inhabiting the newly- colonized areas.
... These defoliation episodes alter ring width formation of host larch trees and dendrochronological methods have been used to reconstruct the timing of historical outbreaks over the past 1,200 years (Büntgen et al. 2009;Esper et al. 2007;Rolland et al. 2001;Weber 1997). Surprisingly, the amplitude of regular LBM mass outbreaks has been greatly diminished since the early 1980s (Baltensweiler 1993b;Ims et al. 2008;Johnson et al. 2010). The fact that this abrupt cessation of outbreak intensity coincides with unprecedented warming has been noted and hypotheses for causal roles of climate change in the variation of LBM dynamics have been advanced: The temperature-induced optimal altitudinal envelope of LBM outbreak epicenters may have shifted up and down during historical periods of climatic warming and cooling, respectively. ...
Key message
The absence of larch budmoth outbreaks and subsequent
consequences on tree rings together with a distinct climate–growth relationship enhance the dendroclimatic potential of larch ring width data from the Tatra Mountains.
Abstract
Regular population oscillations are generally considered to arise from trophic interactions, though it is unclear how such cycles are affected by biotic and abiotic factors. Cyclic outbreaks of the larch budmoth (LBM; Zeiraphera diniana), perhaps the most prominent example of periodic insect population dynamics, leave distinct “fingerprints” in the annual rings of host trees, and have been reconstructed over 1,200 years in the European Alps. Although LBM individuals are known to exist in other regions, it is unclear whether recurrent mass outbreaks historically occurred elsewhere. Here, we present new larch (Larix decidua) host and pine (Pinus cembra) non-host chronologies from the Slovakian Tatra that comprise 323 ring width samples dating back to 1612 AD. May–June and May–July temperatures control larch and pine growth (r
1951–2011 = 0.63 and 0.57; p < 0.001), respectively. LBM outbreak-induced defoliation patterns and subsequent ring width reductions were absent over the past three centuries, during which larch (host) and pine (non-host) growth was significantly synchronized (r
1725–2012 = 0.48; p < 0.001). Spatially limited host forests of overall low stand densities along the northwestern Carpathian arc together with a relatively warm climate envelope are most likely responsible for the absence of cyclic LBM outbreaks. Tree-ring chronologies from these ecotones, free of pulsed disruptions, therefore, represent unique paleoclimatic archives ideal for reconstructing interannual to multi-centennial variations in Eastern European summer temperature.
... Two main hypotheses, both acting in a delayed density dependent manner, have been put forward to explain the population cycles of the larch budmoth. The first one is based on changes in the food quality of the host tree, the larch (Larix decidua Mill) (Baltensweiler 1993). Larch trees suffering from defoliation lack nutrient resources, leading to low-quality needles for several consecutive years. ...
It is 100 years since the first paper described the multiannual cycles in Arctic rodents and lagomorphs. The mechanisms driving population cycles in animals like lemmings and voles are complex, often attributed to extrinsic factors, such as food availability and quality, pathogens, parasites and/or predators. While extrinsic factors provide insights into population cycles, none fully explain the phenomenon. We propose an underlying innate, intrinsic mechanism, based on epigenetic regulation, that drives population cycles under harsh arctic conditions. We propose that epigenetically driven phenotypic changes associated with sexual development, growth and behaviour accumulate over time in offspring, eventually producing a phase change from rising population density to eventual population collapse. Under this hypothesis, and unlike previous hypotheses, extrinsic factors modify population cycles but would not be primary drivers. The interaction between our intrinsic cycle and extrinsic factors explains established phenomena like delayed‐density dependence, whereby population growth is controlled by time‐dependent negative feedback. We advocate integrating a century of field research with the latest epigenetic analysis to better understand the drivers of population cycles.
In this paper, we study some dynamics concerning the interaction of budmoth and plant quality index of larch situated in the Swiss Alps. Taking into account this interaction, a two-dimensional discrete-time system is formulated and discussed. The new model is formulated with an application of Holling type III functional response for the plant quality index. Furthermore, the proposed functional response is supported by actual observed data related to larch budmoth interaction. In addition to proving that solutions are uniformly bounded, the existence of biologically feasible fixed points and the local dynamics of the proposed model regarding its fixed points are also studied. It is shown that the proposed model undergoes period-doubling bifurcation around its coexistence with the implementation of the center manifold and normal form theories. Furthermore, the existence and direction of Neimark–Sacker bifurcation about positive fixed point are discussed. Taking into account the biological relevance of chaos control strategies, different methods of controlling chaos are implemented with their biological relevance. Numerical simulation is demonstrated to illustrate the theoretical discussion. Finally, theoretical discussion is validated with experimental and field data.
Pollinator biodiversity loss occurs at unprecedented rates globally, with particularly sharp declines documented in the North Temperate Zone. There is currently no consensus on the main drivers of the decline. Although climate change is expected to drive biodiversity loss in the future, current warming is often suggested to have positive impacts on pollinator assemblages in higher latitudes. Consequently, pollinator conservation initiatives in Europe and the USA tend to lack climate adaptation initiatives, an omission of which may be risky if climate change has significant negative impacts on pollinators. To gain an understanding of the impacts of climate change on pollinator biodiversity in the Northern Hemisphere, we conducted a literature review on genetic, species and community level diversity. Our findings suggest that global heating most likely causes homogenization of pollinator assemblages at all levels of pollinator biodiversity, making them less resilient to future stochasticity. Aspects of biodiversity that are rarely measured (e.g. genetic diversity, β-diversity, species evenness) tend to be most affected, while some dimensions of climate change, such as fluctuations in winter weather conditions, changes in the length of the vegetational season and increased frequency of extreme weather events, that seldom receive attention in empirical studies, tend to be particularly detrimental to pollinators. Negative effects of global heating on pollinator biodiversity are most likely exacerbated by homogenous and fragmented landscapes, widespread across Europe and the US, which limit opportunities for range-shifts and reduce micro-climatic buffering. This suggests the need for conservation initiatives to focus on increasing landscape connectivity and heterogeneity at multiple spatial scales.
While populations of all animals fluctuate in density, some cycle on a regular basis. Forest Lepidoptera, snowshoe hares, and red grouse cycle with an approximate 10-year periodicity, while voles and lemmings in some areas, cycle with a 3–5-year periodicitiy. Cyclical dynamics can be synchronized over tens to hundreds of kilometers. Predators and social behavior are the primary causes of small mammal cycles and parasitoids and/or disease are the dominant drivers of Forest Lepidoptera cycles. Red grouse cycles are associated with aggressive behavior of males and infection by a nematode. What causes the variation in peak and trough densities between cycles, the transition from decline to increase phase, and synchronizes fluctuations remains a mystery.
We study the dynamics of a discrete-time tritrophic model which mimics the observed periodicity in the population cycles of the larch budmoth insect which causes widespread defoliation of larch forests at high altitudes periodically. Our model employs q-deformation of numbers to model the system comprising the budmoth, one or more parasitoid species, and larch trees. Incorporating climate parameters, we introduce additional parasitoid species and show that their introduction increases the periodicity of the budmoth cycles as observed experimentally. The presence of these additional species also produces other interesting dynamical effects such as periodic bursting and oscillation quenching via oscillation death, amplitude death, and partial oscillation death which are also seen in nature. We suggest that introducing additional parasitoid species provides an alternative explanation for the collapse of the nine year budmoth outbreak cycles observed in the Swiss Alps after 1981. A detailed exploration of the parameter space of the system is performed with movies of bifurcation diagrams which enable variation of two parameters at a time. Limit cycles emerge through a Neimark-Sacker bifurcation with respect to all parameters in all the five and higher dimensional models we have studied.
Periodic outbreaks of the larch budmoth Zeiraphera diniana population (and the massive forest defoliation they engender) have been recorded in the Alps over the centuries and are known for their remarkable regularity. But these have been conspicuously absent since 1981. On the other hand, budmoth outbreaks have been historically unknown in the larches of the Carpathian Tatra mountains. To resolve this puzzle, we propose here a model which includes the influence of climate and explains both the 8-9 year periodicity in the budmoth cycle and the variations from this, as well as the absence of cycles. We successfully capture the observed trend of relative frequencies of outbreaks, reproducing the dominant periodicities seen. We contend that the apparent collapse of the cycle in 1981 is due to changing climatic conditions following a tipping point and propose the recurrence of the cycle with a changed periodicity of 40 years-the next outbreak could occur in 2021. Our model also predicts longer cycles.
Cyclic dynamics are observed in many rodents. In a first step, single explanations were searched for explaining all cycles. However, more local studies have shown that causes of cycles are often different depending on the species or the habitat concerned. It is therefore important to work at a local level to understand the specific dynamics shown by cyclic populations. In this thesis, I sought to understand the cyclical dynamics of voles in the agricultural plains of western France. Three axes were mainly addressed: 1) the structure of density dependence; 2) The changes in demographic traits (survival and reproduction) responsible for the different phases of the cycles; 3) The relationships between demographic traits and agriculture. Modeling approaches, analysis of empirical data and experimental data were used. The main results are that the vole cycles show two density dependent phases. The decline phase takes place in winter and is due to a reproduction change through direct density dependence. The second is the low phase. The latter is probably multifactor and due to delayed density dependence mechanisms. Finally, we have shown that agricultural practices and crop type had a strong impact on the demographic traits and those depend on the season. This thesis gives a consistent pattern explaining how our common vole population enter and maintain cyclic dynamic. However, the underlying mechanisms remain unclear. In this context, some works have been initiated concerning research of maternal effects or resource depletion.
This chapter discusses ecological processes that take place on a wide range of spatial and temporal scales, and is evident that the choices of scales will influence our perception about their dynamics. It is of particular importance to consider extended spatial scales in insects because they are usually winged, and hence often have considerable power of movement by flight. Lygaeus equestris utilizes two kinds of habitats during its yearly cycle, namely, breeding and hibernation sites. Breeding takes place in stands of the host plant V. hirundinaria. Vincetoxicum hirundinaria is a very long-lived perennial plant, and the plant patches change in size very slowly. Plant patches are of widely different sizes and so are the abundances of their local insect populations. Populations of L. equestris are affected by density-dependent factors during the summer, but not during the rest of the year. Flight is essential for L. equestris to track its variable environment. Flight activity during the breeding season is also affected by food conditions. Studies of insect population dynamics have had a strong focus on leaf,phloem feeders, or gall-makers on abundant plants. Population density of L. equestris fluctuates in a wavelike pattern with two peaks and two lows during 18 years. All field population studies are unique to some degree. Any sequence of years has a particular history. The population dynamics of the seed-feeding bug Lygaeus equestris in Sweden takes place in a landscape with habitat patches determined by food resources, microclimate, and seasonal change.
The phenology of many species is shifting in response to climatic changes, and these shifts are occurring at varying rates across species. This can potentially affect species' interactions and individual fitness. However, few studies have experimentally tested the influence of warming on the timing of species interactions. This is an important gap in the literature given the potential for different direct and indirect effects of temperature via phenological change.
Our aim was to test the effects of warming on the western tent caterpillar ( Malacosoma californicum pluviale ). In addition to the direct effects of warming, we considered the two primary indirect effects mediated by warming‐driven changes in its host plant, red alder ( Alnus rubra) : changes in resource availability due to phenological mismatch (i.e. changes in the relative timing of the interaction), and changes in resource quality associated with leaf maturation.
We experimentally warmed egg masses and larvae of the western tent caterpillar placed on branches of red alder in the field.
Warming advanced the timing of larval but not leaf emergence. This led to varying degrees of phenological mismatch, with larvae emerging as much as 25 days before to 10 days after the emergence of leaves. Even the earliest‐emerging larvae, however, had high survival in the absence of leaves for up to 3 weeks, and they were surprisingly resistant to starvation. In addition, although warming created phenological mismatch that initially slowed the development of larvae that emerged before leaf emergence, it accelerated larval development once leaves were available. Therefore, warming had no net effect on our measures of insect performance.
Our results demonstrate that the indirect effects of warming, in creating phenological mismatch, are as important to consider as the direct effects on insect performance. Although future climatic warming might influence plants and insects in different ways, some insects may be well adapted to variation in the timing of their interactions.
During the late 1940s, immediately after World War II, the lush green forests of the Engadine Valley, high in the Swiss Alps, turned an ugly red-brown in the midst of the tourist season. This was due to a spectacular outbreak of the larch budmoth, Zeiraphera
diniana Guenée (Lepidoptera: Tortricidae). Preparing for a revival of the tourist industry, and having the new insecticide DDT at hand, it seemed only appropriate that the tourist office urge the forest service to control the pest. This was the beginning of what was to become a 34-year study of the population dynamics of the larch budmoth (Fig. 1).
The grey larch budmoth, Zeiraphera griseana Hb., defoliates the extensive larch forests of the European Alps at intervals of from six to eight years. Historical records on the development of visible damage for ten gradations, together with quantitative results on the population dynamics of the last full gradation, provide the explanation of this cyclic phenomenon. Average weather conditions allowing a steady population increase, the deciduous habit of the host tree, and a high rate of increase constitute a simple ecological situation which results in regular oscillations of populations of this insect.
Studies on the bionomy and gradology of the grey larch Tortricid, Zeiraphera diniana Gn. in Middle Suisse. Part 2: Life tables and origin of the moths of the second generation.
The most important regulating factors were a. animals predating eggs and larvae, b. insufficient adaptation of the larvae to food and climate as well as of the prepupae and pupae to soil. The index of propagation during 3 generations amounted to about 0.7. For this the population of Z. diniana in Middle Suisse can exist only by immigration of moths of the second generation from the areals southern and southwestern which are optimal for the pest.
Der Lärchenwickler, Zeiraphera diniana Gn., bevölkert nicht nur die subalpinen Lärchen-Arven-Mischwälder, wo er zwischen 1600–2000 m ü. M. zyklische Massenvermehrungen durchläuft, sondern ist auch latent im schweizerischen Mittelland vorhanden. In ersten Un-tersuchungen wurde versucht, vor allem die Phaenologie und die Lebenstafel der latenten Population in Lenzburg (Kanton Aargau) etwas zu erhellen.
Studies on the bionomy and gradology of the grey larch Tortricid, Zeiraphera diniana Gn. in Middle Suisse. 1: Biotop, phenology and population dynamics. The larch bud moth, Zeiraphera diniana Gn. (Lep.: Tortricidae), exhibits a cyclic fluctuation in numbers, in the subalpine larch-cembran pine forest above 1600 m causing extensive defoliation to the larch at 9-year intervals, but remains more or less stable at low densities in larch plantations within the beech-oak forest on the Swiss Plateau at 500 m. The development of the various stages was established and showed the existence of two independent moth flights; one in June and the second in August. The latter is almost undoubtedly due to immigration from the optimum areas at higher altitudes. Life table studies for 4 generations allow the following statements:
Provided that the low coefficient of reproduction of 0.7 is generally valid, the bud moth population on the Swiss Plateau could not survive without repeated immigration from high altitudes.
Negative feed-back by competition for food and space, and by cyclic induced changes in the nutritional base as regulatory principles in the population dynamics of the larch budmoth Zeiraphera diniana (Guenée). At high density of the larvae of Z. diniana on larch trees in subalpine forests, intraspecific competition causes an increase in mortality of larvae and pupae, as well as reduction of pupal weight and fecundity of the emerging moths. The negative effects become more pronounced by shortage of food at population levels leading to complete defoliation of the larch trees. Defoliation in turn activates specific mechanisms in the trees, which lead to late and slow sprouting of the needles in spring (weak coincidence), short needles (reduced mass of nutritional base), and reduced quality of the needles (elevated contents of fibres and reduced protein contents). Thus the succeeding bud moth populations are depressed by negative feed-back. The cyclic numeric fluctuations with a periodicity of 8 to 10 years, which are characteristic of populations of Z. diniana in its optimum area, may thus be regarded as the expression of an autoregulating life system in which the species multiplies for 4–5 generations under favorable conditions and thus, transgressing the carrying capacity, changes the nutritional base in such a way that environmental resistance to the species becomes high for another 4 generations.
Im Hinblick auf eine Erklärung der zyklischen Massenwechsel des Lärchenwicklers Z. diniana in den subalpinen Arven-Lärchenwäldern wurde der Einfluß der Populationsdichte, besonders aber der Nahrungsgrundlage auf Vitalität und Fekundität des Schädlings untersucht. Die Untersuchungen führten zu folgenden Ergebnissen:
Diese Mechanismen steigern die Raupenmortalität im 1. und 2. Nachschadensjahr auf 80–90% und bewirken weiterhin eine stark reduzierte Fekundität.
Plant ecologists such as C.L.Willdenow(1765-1812), F.H.A.von Humboldt(1769-1859), A.Grisebach(1814-1879), and A.F.W.Schimper(1856-1901) noted that plant form and leaf habit(evergreen vs. deciduous) were associated with specific environments. These early observations prompted a myriad of studies to investigate the relation between leaf habit and environment and evolutionary advantage of different growth forms. Interest in the relationship between environment and leaf habit continues today(Chabot & Hicks 1982; Woodward 1987).
The expansive boreal forests in the northern hemisphere are typically characterised by evergreen trees(Wolfe 1979). The dominance of evergreen trees in harsh forest environments has been attributed to the greater annual net carbon gain(Mooney 1972; Schulze et.al.1977; Waring & Franklin 1979) and more efficient use of nutrients(Chapin 1980; Loveless 1961; Waring & Franklin 1979) by evergreen trees compared to species with a deciduous leaf habit. The greater leaf longevity of evergreens has been suggested to reduce the annual carbon and nutrient requirment to produce new foliage(Chabot & Hicks 1982). Needle longevity of evergreen trees in boreal and subalpine forests may exceed several decades and has been reorted to be as long as 40 years for bristlecone pine Pinus aristata(Ewers & Schmid 1981). The conservative use of of nutrients by trees in boreal and subalpine forests is particularly important, because nutrient availability is low due to adverse effects of low soil temperature on decomposition, mineralisation, and nutrient and water uptake. Also, long cold winters and short cool summers limit leaf growth and net photosynthetic rates of trees in these forests.
Larches, deciduous needle-leaf gymnosperms in the genus Larix, however, are common components in many cold-temperate and boreal forests in the Northern Hemisphere. Even at the northern and altitudinal limits for tree growth, larches are widespread and often dominate a woodland zone north of evergreen dominated boreal forests or above subalpine forests(Richards 1985; Richards & Bliss 1986). The widespread occurrence of larches in subalpine and boreal forests is an intriguing puzzle given the concept that the evergreen habit is more advantageous in harsh environments. Larches therefore must possess physiological and morphological characteristics that enable them to survive, grow, and reproduce as deciduous conifers in environments where evergreens normally dominate. Hence, it appears that larches are successfully living in what is normally considered an evergreen world.
Because larch needle morphology, canopy architecture, and water-conducting system anatomy closely resemble those of evergreens gymnosperms(table 1), comparative studies between these two groups rpovide insight of the effect of leaf habit on photosynthetic rate, foliage mass, nitrogen and water use, and annual net carbon gain. Comparative studies between evergreen and deciduous angiosperms may also be useful, but such as review is beyond the scope of this article. We include in this article both ecophysiological and stand-level studies, when available, to compare carbon gain and nutrient and water use of larches and sympatric evergreen conifers.
Thesis (doctoral)--Ecole polytechnique fédérale de Zurich, 1965.
Ergebnisse zw61fj/ihriger quantitativer Untersuchun-gen der Populationsbewegung des Grauen L/irchenwicklers Zeiraphera griseana Hfibner (=diniana Guen6e) im Ober-engadin (1949-1960) Eidg Anst Forstl Versuchswes Mitt
- Auer
Auer C (1961) Ergebnisse zw61fj/ihriger quantitativer Untersuchun-gen der Populationsbewegung des Grauen L/irchenwicklers Zeiraphera griseana Hfibner (=diniana Guen6e) im Ober-engadin (1949-1960) Eidg Anst Forstl Versuchswes Mitt 37 : 173-263
Eidg Anst Forstl Versuchwes Mitt Zeiraphera griseana Hiibner (Lepidoptera: Tortricidae) in the European Alps. A contribution to the prob-lem of cycles The r61e of migration for the population dynamics of the larch bud moth
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- W Baltensweiter
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Auer C (1977) Dynamik yon L/irchenwicklerpopulationen 1/ings des Alpenbogens. Eidg Anst Forstl Versuchwes Mitt. 53:71-105 Baltensweiler W (1964) Zeiraphera griseana Hiibner (Lepidoptera: Tortricidae) in the European Alps. A contribution to the prob-lem of cycles. Can Entomol 96:792-800 Baltensweiter W, Fischlin A (1979). The r61e of migration for the population dynamics of the larch bud moth, Zeiraphera diniana Gn. (Lep. Tortricidae). Mitt Schweiz Entomol Ges 52:259-271 Baltensweiler W, Fischlin A (1988) The larch bud moth in the Alps.
The larch bud moth in the Alps Dynamics of forest insect populations
- W Baltensweiler
- A Fischlin